This invention relates to a pipe reforming clamp provided with force applying members adapted to be positioned in encircling relation about the rim of a pipe having a noncircular cross-section and reform same to a circular cross-section and, in particular, to a clamp which simultaneously expands and/or contracts the members in such a manner that they rotate from a nonengaging first position defining a first circle and to a pipe engaging second position defining a second circle.
In typical pipe or cylindrical vessel fit-up clamps, the vessel may be made round by the use of a large number of individual adjusting screws each having its axis aligned with a radius from a longitudinal axis generally representing the pipe axis. Such an arrangement is shown in U.S. Pat. No. 3,952,936 issued Apr. 27, 1976. Separately adjusting these screws can be very time-consuming and even with great care it might be impossible to get the vessel rim truly round. Further, these screws cannot be rapidly reset for another like pipe of somewhat different diameter since the screws are set for a given pipe. It would be desirable to have a clamp which is not unduly time-consuming to use and reduces to a minimum the number of adjustments necessary to achieve roundness.
In this invention, a clamp is adapted to encircle the end portion of a pipe and comprises a rigid annulus having a circular inside opening defined by a diameter greater than the exterior diameter of the pipe to be encircled, and a plurality of generally equiangularly spaced, force applying assemblies each having a force applying portion and carried by the annulus, and a drive arrangement for driving the portions into and out of forcible engagement with the pipe exterior. In particular, the clamp is characterized by the annulus comprising a pair of unitary rings interconnected in parallel relation, the force applying assemblies being pivotally mounted between the rings each having a roller at an inward radial end and a toothed sprocket at an outward radial end, the pivot axes defining a circle the center of which generally centered with the pipe axis, and the drive arrangement including a drive chain connected to the assemblies for simultaneously pivoting the rollers from a first position defining a first circle to a second position defining a second circle, the two positions of the rollers defining concentric circles having the same center as the circle passing through the pivot axes. The drive chain is interconnected to the sprocket of each force applying assembly whereby driving movement of the chain will cause the rollers to pivot about their axes, simultaneously, causing the rollers to contract radially inwardly or expand radially outwardly to define the circles which will encircle and either engage or disengage with the pipe.
Further, an adjustment arrangement locally of individual force applying assemblies includes a sprocket wheel which is driven radially inward against the chain to change the inward radial position of each roller and thus change the relative positions of the rollers to each other. Thus the rollers could define a perfect circle, an ellipse or some other shape should it be desirable.
An advantage of such a clamp is the ability to achieve roundness in a pipe to be welded with a minimum of effort but with a maximum of diametral accuracy and to accommodate pipe of different diameters within the range of the clamp.
Another advantage of a clamp having a contracting opening is that a multitude of force applying members can be adjusted to a certain position relative to the others, such as where each roller is positioned to be tangent to a circle, then with the turning of a drive gear, the rollers will still define a circle, with great precision, over a wide range of diameters.